Cutting metals such as an iron, aluminum, and various types of alloys, and nonmetals such as glasses, ceramics, special earthenware and reinforced plastics is one of the working processes for removing unnecessary parts from a workpiece with the use of a cutting tool to provide a desired shape, size or surface to the workpiece. In any cases of cutting, big friction occurs between a workpiece and a tool. Frictional heat burns the tool and makes the machined surface of the workpiece rough, and thermal expansion lowers the accuracy of the shape and the size of the workpiece and the tool, thus causing various problems. To reduce the above problems, a cutting fluid or a lubricant has been employed in cutting.
Water-soluble and water-insoluble cutting oils are commonly used as a cutting fluid or a lubricant to cut metals. A typical example of water-insoluble cutting oils is an oil solution including mineral oil, sulfur, and chlorine. The disadvantage of the oil solution is that it can be used only when the cutting temperature is low because high cutting temperature may cause the production of fire and smoke. In the meanwhile, a water-soluble cutting oil including mineral oil and the like, to which soap and sulfate are added as an emulsifier or higher alcohol and fatty acid ester are added as a binder, can be used. It is generally used after being diluted with water. Such a water-soluble cutting oil has an excellent lubricity, but on the other hand, it has low cooling property.
Water-insoluble cutting oils can be used repeatedly in cutting operation. However, the bacteria propagates in cutting oil as time goes by, and the cutting oil gives off a bad smell by the bacteria itself or the gas produced by the bacteria. The disposal of the used cutting oil has become the serious problem because the oil and emulsifier in the cutting oil inflicts a bad influence on the environment when said fluid is discharged as a waste liquid.
To prevent decay and offensive smell, antiseptic agent, mildewproof agent, and/or antibacterial substances such as amine, amide, amino acid have been added to water-soluble cutting oil. However, these agents and substances lower the quality of water-soluble cutting fluid as oil solution.
One of the objectives of the present invention is to provide a water-soluble cutting fluid, which is mainly used to cut metals and nonmetals, has an excellent lubricity and cooling property, prevents abrasion of a cutting tool, and can extend service life of a tool.
Another objective of the present invention is to provide a water-soluble cutting fluid, which can be used a number of times, does not provide a nutrient media for bacteria growth, and does not include environmentally-hazardous substances.